JP2001519266A - Method and apparatus for determining the state of light in front of a moving object, for example in front of a car - Google Patents

Abstract

(57) [Summary] The present invention relates to a method for determining the state of light in front of a moving object, for example, in front of an automobile. In this case, a sensor unit is provided, which runs in the region (20) in the running direction in front of the vehicle, and is further provided with an evaluation unit, which evaluates the value provided by the sensor unit In addition, the general light state and the light state in the traveling direction ahead of the vehicle are captured. According to the invention, the luminance measurement is carried out by a planar image sensor and, on the lane (3) between the lane edges (4, 5), the sections (7, 71) respectively taken into account by the image sensor. , 72, 73) are evaluated section by section and / or globally to provide one or more information about the state of the light, for example the state of the light in front of the entrance to the tunnel (6). Generate a value.

Description

DETAILED DESCRIPTION OF THE INVENTION

The invention relates to a method for monitoring and estimating the state of light in front of a moving object, for example in front of a motor vehicle, according to the preamble of claim 1.

In the case of a device of this type, which is known from German Patent Application DE 195 23 262 A1, a sensor device and an evaluation device are provided for automatic switching of a lighting device in a vehicle. In this case, the sensor device has at least one global sensor that captures the overall light state around the vehicle in a non-directional manner, and a traveling direction sensor that captures the light state in the traveling direction ahead of the vehicle with a directivity. are doing. From the signal of the global sensor, a change in the overall light state around the vehicle can be identified by the evaluation device, for example, at dusk or dawn, and the lighting device can be turned on or off. Also, from the signal of the traveling direction sensor, the evaluation device identifies a tunnel or a road under an overpass or under a guard located in the traveling direction in front of the vehicle, and switches on the lighting device in a timely manner before entering the road. be able to.

[0003] A disadvantage of this device is that with such a device configuration, the provision of a separate ambient sensor and traveling direction sensor results in considerable costs. In this case, photocells are used as light-sensitive elements, and the incident light is guided to those photocells by using an optical focusing device. At that time, there is also a dependency on light shielding and irradiation time.

[0004] According to European Patent Application EP 0736 414, a vehicle is known in which an optical scanning device is mounted laterally for the purpose of contactlessly scanning lateral roadway areas. An evaluation unit is connected downstream of this scanning device. The optical scanning device has a plurality of infrared transmitting elements and an attached CCD array juxtaposed to each other, and scans the road surface for the purpose of capturing lane boundaries. The evaluation unit is also configured to perform a propagation time measurement, a contrast measurement and a contour identification from the data supplied by the scanning device.

[0005] A significant disadvantage of using CCD sensors or linear CMOS sensors for measuring brightness or brightness is that they are limited in the brightness dynamics that they can capture. Therefore, these sensors are provided with an electronic or mechanical irradiation time control device and a light shielding device. For this reason, the irradiation time and the position of the light shielding device must be taken into consideration, and the signal measured on the output side of the sensor cannot be used for absolute luminance measurement.

An object of the present invention is to make it possible to determine the state of light in front of a moving object, for example, in front of a vehicle very easily, and to perform a manual operation or an automatic operation of lighting in front of the moving object according to circumstances by appropriate measures. That is.

Advantages of the invention With respect to the known prior art, the decisive advantage of the method according to the invention with the arrangement according to the characterizing part of claim 1 is that the light in the direction of movement ahead of a moving object, such as a vehicle, for example The point is that the mechanical and electrical complications for determining the state can be significantly reduced. This is generally achieved with significantly lower overall system costs. By realizing position-selective luminance measurement, extraordinary flexibility has been obtained.

According to the invention, basically, in a method for determining the state of light in front of a moving object, for example in front of a vehicle, a brightness measurement is carried out by a planar image sensor and in a section which is respectively taken into account by the image sensor. Evaluating the measured luminance values section-by-section and / or globally forms one or more information values about the state of the light.

[0009] Advantageous embodiments of the method according to claim 1 for determining the state of the light ahead of a moving object, for example in front of a vehicle, are possible with the measures described in the further method claims.

According to a particularly advantageous embodiment of the method according to the invention, a CMOS image sensor is used as the image sensor for determining the brightness in a planar manner. In this case, an image sensor having a non-linear conversion characteristic is preferably used, so that a predetermined current wave or current range, which is often considerably narrow, is optimally used as much as possible even when the dynamics of light incidence is large. be able to.

In a further preferred embodiment of the method according to the invention, a logarithmic or logarithmic image sensor is used for the luminance measurement.

According to a preferred embodiment of the method according to the invention, the luminance measurement is performed by averaging the pixel luminance in a plurality of measurement windows.

According to a particularly preferred embodiment according to the invention, the luminance measurement is combined with lane tracking in order to carry out a desired measurement of the ambient luminance in the lane course.

[0014] According to a further embodiment, object detection or object identification is performed, so that, for example, a large lorry traveling in front of the vehicle can be eliminated in a position-selective brightness measurement. .

According to the device for carrying out the method according to the invention, an essentially planar image sensor is provided, on which an area located in front of the vehicle can be imaged, or The area is imaged. Advantageously CM as a planar image sensor
An OS image sensor is provided, which can be a logarithmic image sensor according to a particularly preferred embodiment. In another embodiment, the image sensor may have a non-linear conversion characteristic curve which is very generally advantageous.

The method according to the invention or the device according to the invention is used particularly advantageously for the following purposes: That is, it is used to proactively warn the driver of the vehicle and alert the driver to switch on the vehicle lighting, or to operate the vehicle lighting proactively and automatically, for example to switch on and possibly It is also used to switch off. In this way, a reaction can be made to the entrance or exit of the tunnel or the road under the overpass or guard in accordance with the situation.

Furthermore, the method according to the invention or the device according to the invention is used with particular advantage for the following purposes: That is, it is used to alert the driver of the vehicle about turning on / off the vehicle lighting based on the ambient brightness obtained by the planar image sensor, or is also obtained by the planar image sensor. It is used for automatically operating the vehicle lighting on the basis of the ambient brightness, for example for switching on and possibly also for switching off. By doing this, during the day,
At night, global darkness caused by clouds, dawn, dusk, etc., reacts to the situation.

Drawings Next, the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 1 is a schematic diagram of a vehicle provided with an image sensor that captures an area located in the traveling direction ahead of the vehicle.

FIG. 2 is a diagram illustrating a scene that occurs in front of the vehicle before entering the tunnel.

FIG. 3 is a block diagram showing components involved in the entire system.

FIG. 1 schematically shows a vehicle 1 provided with an image sensor 2, which captures an area 20 located in the running direction ahead of the vehicle. 1 shows, along the longitudinal axis of the vehicle, a cross-section and an advantageous location for mounting the image sensor 2. This is advantageously as high as possible behind the windshield 11 and in the following places: That is, it is a place where the traffic condition of the area 20 in the traveling direction ahead of the vehicle 1 can be seen well, and the image sensor 2 is also located within the operation range of the wind wiper. Advantageously, the traffic situation located in the area 20 in the direction of travel in front of the vehicle 1 is coupled by a lens arrangement 21 to the light-sensitive surface of a flat or planar image sensor.

FIG. 2 shows an area 20 located in front of the vehicle 1, which is a special scene before entering the tunnel 6. The lane located in front of the vehicle is denoted by reference numeral 3 and its periphery or boundary is denoted by reference numerals 4 and 5. This lane leads to the right half of the entrance to the tunnel 6. In the daytime, only a small ambient brightness or brightness is measured in the area of the tunnel entrance. According to a particular feature of the invention, the area 20 ahead of the vehicle, here the lane course, is divided into special measurement fields 7, which are arranged differently. They include, for example, a global or general large measuring field 71 in front of the vehicle, an intermediate distance measuring window 72 oriented substantially towards the lane 3, and a further oriented entrance to the tunnel 6. Is a measurement window 73 that captures

FIG. 3 shows a block diagram of the basic components involved in the overall system. The entire system can be used in two forms. One basic form is to warn the driver of the vehicle to alert the user to switch on or off the vehicle lighting. The other basic form is to automatically operate the vehicle lighting, for example for the purpose of switching on and possibly switching off the vehicle lighting.

The image sensor 2 supplies a signal relating to a visual appearance of a traffic situation ahead of the vehicle. This signal is supplied to a suitable evaluation unit 8. The evaluation unit generates, from the signal, a warning to the driver or parameters required for lighting control. This can be the course of the lane, the surrounding brightness or brightness, the course of the brightness along the lane 3, or it can be, for example, a special type of object in the course of the lane just before the vehicle 1. To calculate these parameters, an appropriate algorithm or calculation method used in image processing or the like is used. One of the signals calculated and generated in this way is a signal for switching on or off vehicle lighting, which is supplied to the lighting control device 9. This lighting control device 9
Switches the illumination depicted as headlight 10 according to the supplied signal. The other of the signals calculated and generated as described above is a signal for warning the driver. This signal can be generated alternatively or in addition to the automatic switching signal. This signal can cause an appropriate driver alert or driver information to be generated, for example, via a man-machine interface, such as an instrument panel with an illumination status indicator 12. This alerts the driver that the light should be switched on or on. In addition to the image evaluation for measuring the brightness and possibly the image information for identifying the lane, the evaluation unit 8 is preferably connected via other sensors (generally denoted by reference numeral 13). An information signal is provided. This can be, for example, information about the vehicle speed.

According to the present invention, a planar or flat sensor is used as the image sensor 2. Such a planar or flat image sensor is constituted by a number of individual brightness sensors juxtaposed in one plane. In this case, specific points around the vehicle, in particular in the area 20 in front of the vehicle, are imaged on specific light receivers, ie individual brightness sensors in the image sensor 2, so that specific points around the vehicle are obtained. Impression or expression can be obtained. The measurement of the ambient luminance can be performed based on the peripheral image thus formed. The overall brightness of the scene being viewed is determined by appropriately processing the brightness signals of the individual light receivers located within the measurement windows 71, 72 or 73 of the various scenes. In a particularly preferred manner, the luminance measurement can be performed by averaging the pixel luminance, that is, by averaging the corresponding individual signals of the respective light receiver located in the measuring window. .

By comparing with the threshold value in the evaluation unit 8, it is determined whether the surrounding luminance requires lane illumination by the vehicle headlight 10. When the headlights 10 are not switched on, a corresponding appropriate signal can alert the driver that the headlights should be switched on. On the other hand, when it is switched on, the signal can indicate to the driver that the vehicle lighting is no longer necessary and the headlights 10 can be turned off if the ambient brightness is appropriate. In order to avoid frequent occurrence of opposite instructions, the judgment threshold value for turning on / off the lighting is made to have a hysteresis.

[0028] Unlike an individual luminance sensor such as a single photo element, the flat image sensor 2 provided according to the present invention enables a position-selective luminance measurement that is subdivided for the entire scene to be observed. Become. By evaluating the signal of a specific pixel, the luminance in a predetermined image area can be measured. When the image sensor is arranged as depicted in FIG. 1, the image sensor captures a scene located in front of the vehicle 1. If the image sensor 2 is combined with lane identification in accordance with an advantageous embodiment of the invention, the driving course of the vehicle 1 can be described. In the depiction according to FIG. 2, the intended brightness measurement is performed in the area along the lane 3 to be measured. According to an advantageous embodiment, each image window 71, arranged along a specific area or lane 3
At 72 and 73, a measurement of brightness or brightness is performed. Note that the measurement window does not need to be rectangular. Also, an advantageous measurement of the luminance profile is performed by averaging the luminance values of the pixels in the individual measurement windows.

Thus, for example, at the measurement window 73 located just before the entrance to the tunnel 6 as shown in FIG. 2, too little brightness may be measured. Thus, it is possible to request the driver to switch on the lighting of the vehicle before entering the tunnel 6. By arranging the vehicle accordingly, it is also possible to switch on the lighting of the vehicle automatically. In addition, the switch-off process is not performed at an early stage, and is performed only when sufficient luminance can be measured even in a scene area in front of the vehicle. In addition, additional information from the sensor 13, for example a sensor representing the vehicle speed, can be used to improve the detection process. For example, a large measurement window 71 extending over the entire scene may be used to identify global brightness or brightness conditions such as those caused by night, daytime, dawn or dusk, darkening due to clouds or tree-lined roads, and the like.

Thus, according to the invention, a luminance measurement is performed by the planar or flat image sensor 2 and is formed in the respective appropriately associated sections, for example by the individual light receivers of each measuring window. In one of the measurement windows 71, 72, 73, one or more information values relating to the state of the light are generated by utilizing the evaluation of the luminance values by the sectors measured by the image sensor 2 and / or globally or globally. Is done. Great flexibility can be obtained by the position-selective luminance measurement obtained in this way.

A position-selective luminance measurement of the type according to the invention can be further improved by using object identification. In this case, an object existing in front of the vehicle is identified by an image evaluation method having one or two cameras operating simultaneously. That is, for example, it is possible to detect that a large lorry or other passenger car is traveling in front of or in front of its own vehicle. Because the vehicle may be painted significantly darker or lighter in some cases, global or sector brightness measurements may be confused. This is especially true when the object is located at a small distance in front of its own vehicle and fills the area 20 to a greater or lesser extent, occupying almost the entire image area of the image sensor 2. It is when you are. For this reason, the luminance measurement can be corrected by the object identification so as to restrict only the area other than the identified object to avoid erroneous measurement.

A CMOS image sensor is used as the image sensor 2. In this case, it is advantageous to use a logarithmic image sensor, that is, a logarithmic image sensor. The logarithmic profile of the light intensity and the current or voltage conversion curve ensures that the contrast resolution over the entire luminance region remains constant. Thereby, the calculation of the image processing performed in the evaluation unit 8 is simplified. Logarithmic image sensors of this kind are known, for example, from Institut fuer Mikroelektronik Stuttgart (IMS), Allmandr
ing 30a, in D-70569 Stuttgart, which is HDRC2-EC (Hi
ght-Dynamic-Range CMOS Evaluation Camera). Obviously, other image sensors having a non-linear conversion characteristic curve, such as an exponential function or other profile, can be used. What is important is that when converting the light intensity into a current signal or a voltage signal, the best possible use is made of the often small area which arises there. In other words, the rise of the conversion characteristic curve should be reduced as the intensity of light arriving at the image sensor increases, so that the magnitude of the current signal or the voltage signal becomes smaller as the intensity of light increases. Should be increased. That is, it is possible to form an image in a larger luminance range in the current region or the voltage region having the same size as compared with the linear characteristic curve. Therefore, the luminance dynamics of the image sensor increases.

The method and the device according to the invention can be used for the purpose of proactively alerting the driver of a vehicle and alerting the user to switch on the vehicle lighting or to automatically operate the vehicle lighting proactively. For example, it is used to switch on and possibly switch off. Therefore, according to the present invention, it becomes possible to react to a tunnel appearing in front of the vehicle or a road under an overpass or a guard in a situation-specific manner.

Alternatively and optionally additionally, the method and the device according to the invention are used for the following purposes: That is, it is used for the purpose of alerting the driver of the vehicle about turning on / off the vehicle lighting based on the surrounding luminance obtained by the planar image sensor 2 or is also obtained by the planar image sensor 2. It is used for the purpose of automatically operating the lighting of the vehicle based on the ambient brightness, for example for switching on and possibly switching off. Therefore, according to the present invention, it is possible to respond to the surrounding luminance that changes for various reasons in accordance with the situation.

A particular advantage of the present invention is that it allows automatic measurement of the distribution of brightness in the direction of travel. However, measuring the surrounding brightness also allows for brightness in a specific area around the vehicle. Based on such information values, the driver can be instructed on the operation of the lighting, or in some cases, can automatically operate the lighting. Advantageously, the brightness is measured position-selectively according to the invention. Further, for example, by combining with lane transition identification and / or object identification, it is possible to proactively determine the luminance transition characteristic in the lane. With this,
Roads under tunnel entrances and overpasses or under guards that appear during the course of travel can be considered early.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a vehicle including an image sensor that captures an area located in a traveling direction ahead of the vehicle.

FIG. 2 is a diagram illustrating a scene that occurs in front of a vehicle before entering a tunnel.

FIG. 3 is a block diagram showing components involved in the entire system.

Claims (9)

[Claims] 1. A method for determining a state of light in front of a moving object, for example, in front of an automobile, comprising a sensor unit, which scans an area in the traveling direction in front of the vehicle, and is provided with an evaluation unit. Wherein the evaluation unit determines, from the values supplied by the sensor unit, the state of the light in front of the moving object in a form that captures both the general state of the light and the state of the light in the direction of travel in front of the vehicle. One is related to the state of the light by performing a luminance measurement with a planar image sensor and evaluating the luminance values measured in sections correspondingly considered by the image sensor section by section and / or globally. Or an image sensor that generates a plurality of information values and performs logarithmization of the planar image sensor or an image sensor having a non-linear conversion characteristic Wherein, determining the status of the moving object in front of the light to be. 2. The method according to claim 1, wherein a CMOS image sensor is used as the image sensor for the planar measurement of the luminance. 3. The method according to claim 1, wherein the luminance measurement is performed by forming an average value of pixel luminances in a plurality of measurement windows. 4. The method as claimed in claim 1, wherein the luminance measurement is combined with automatic lane following to perform a desired measurement of the ambient luminance in the course of the lane. 5. The method as claimed in claim 1, wherein the luminance measurement is combined with the object identification to identify a special object in the lane course, for example a lorry, and to take into account the luminance measurement. 6. Apparatus for performing the method according to claim 1 or 2 to 5, wherein a planar image sensor (2) is provided, on which the image sensor is arranged. Vehicle (1)
An area (20) existing in front is imaged, and an evaluation unit (e.g., for evaluating the brightness value section by section and / or globally)
8) and an image sensor that performs logarithmic conversion or an image sensor (2) that has non-linear conversion characteristics as the image sensor (2). 7. The device according to claim 6, wherein a CMOS image sensor is provided as the planar image sensor. 8. The method according to claim 1, wherein the method further comprises proactively giving a warning to the driver of the vehicle.
Used to alert (11, 12) about switching on the vehicle lighting (9, 10) or to automatically operate the vehicle lighting (9, 10) proactively, for example by switching on and possibly Is used to switch off. 9. The method as claimed in claim 1, wherein the driver of the vehicle (1) is determined by a planar image sensor (2). Based on the ambient brightness, it is used to call attention to turning on / off the vehicle lighting (9, 10), or it can also be used as a planar image sensor (2).
A) for automatically operating the vehicle lighting (9, 10), for example for switching on and possibly also switching off, based on the ambient brightness determined according to (1).